Yes but not how they are doing it now.

For an average item for a level, it should have a slot cost of zero. Now if there were better items (like blue, purple, or gold) it would have a higher cost. So using the current system, maybe all normal items have a zero cost however if the item is +1, its slot cost would go up one. If it is +3 its cost would be 3. So in the end, you could have 4 +3 rings, but everything else would have to be normal... or something like that.